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F120R/F100R/F80R - Open Bath Damper

Installing Your Fork | Before You Ride | Setting Sag | Adjusting Rebound | Service Intervals | Important Safety Information


F120 R: 4.7 in./120 mm
F100 R: 3.9 in./100 mm
F80 R: 3.1 in./80 mm


air spring pressure, rebound

spring/damper type

air/open bath

intended use


Installing Your Fork

Be sure your fork is properly installed before proceeding. Clicking on the link above will take you to a new page. If your fork came pre-installed on your bicycle, continue to the next section, Adjusting Rebound.

Before You Ride

  1. Check that quick-release levers are properly adjusted and tightened.
  2. Clean the outside of your fork with only mild soap and water, and wipe dry with a soft dry rag.

    Note:  Do not use any solvents or de-greasers, as these products can cause serious damage to paint and anodized parts (upper tubes, knobs, steerers).

    Do not spray water directly on the seal/upper tube junction. Do not use a high pressure washer on your fork.

  3. Inspect entire exterior of fork for damage. The fork should not be used if any of the exterior parts appear to be damaged. Please contact your local dealer or FOX Racing Shox for further inspection and repair.
  4. Check headset adjustment. If loose, adjust according to manufacturers recommendations.
  5. Check that brake cables or hoses are properly fastened.
  6. Check that the front and rear brakes operate properly on flat land.

Setting Sag

You can also view a Flash video on Setting Sag.

To get the best performance from your fork, it is necessary to set and adjust sag. Generally, sag should be set to 15–25% of total fork travel.

  1. Unscrew the blue aircap (shown below) on top of the left fork leg to expose the Schrader valve.

  2. Attach a FOX Racing Shox High Pressure Pump to the Schrader valve.
  3. Using the Air Spring Settings table below, pump your fork to the appropriate setting using the FOX High Pressure Pump, then remove the pump.
  4. Install a zip tie with light friction on the upper tube and push it down until it contacts the fork seal.
  5. Carefully sit on the bike and assume a normal riding position. The fork should compress slightly.
  6. Being careful not to further compress the fork, dismount the bicycle. Measure the distance between the seal and the zip tie. This distance is sag.
  7. Compare your sag measurement to the Sag Setup table below.

    If your sag is lower than on the table
    , screw on the pump fitting, note the current air pressure setting and depress the black bleed-valve to reduce the gauge pressure by 5 psi. Measure sag again and repeat adjustment, if necessary.

    If your sag is higher than on the table
    , screw on the pump fitting, note the current air pressure setting and pump to increase the gauge pressure by 5 psi. Measure sag again and repeat adjustment if necessary.
  8. Screw the blue aircap back on, and go ride.

    Air Spring Setting Guidelines

    Rider Weight

    Air Pressure

    < 125 lbs.

    45 psi

    125 - 135 lbs.

    50 psi

    135 - 145 lbs.

    55 psi

    145 - 155 lbs.

    65 psi

    155 - 170 lbs.

    75 psi

    170 - 185 lbs.

    85 psi

    185 - 200 lbs.

    95 psi

    200 - 215 lbs.

    105 psi

    215 - 230 lbs

    115 psi

    230 - 250 lbs.

    125 psi

    Sag Setup


    XC/Race FIRM

    All-Mountain PLUSH

    80 mm (3.50")

    12 mm (0.50")

    20 mm (0.75")

    100 mm (3.90")

    15 mm (0.62")

    25 mm (0.98")

    120 mm (4.70")

    18 mm (0.69")

    30 mm (1.19")

    140 mm (5.50")

    21 mm (0.81")

    35 mm (1.38")

    150 mm (5.90")

    23 mm (0.91")

    38 mm (1.50")

    Sag Troubleshooting



    Too much sag

    (+) air pressure in 5 psi increments

    Too little sag

    (-) air pressure in 5 psi increments

    Excessive bottoming

    (+) air pressure in 5 psi increments

    Harsh ride; full travel not utilized

    (-) air pressure in 5 psi increments

Adjusting Rebound

The rebound knob (shown below) is located on the top of the right fork leg, and has 12 clicks of adjustment. Rebound controls the speed at which the fork extends after compressing. Turning the knob clockwise slows down rebound; turning the knob counterclockwise speeds up rebound. As a starting point, turn the rebound adjuster knob all the way clockwise (full in) until it stops, then turn counterclockwise (out) 6 clicks.

Knob Setting
(clicks out from full in)

Setting Description

Tuning Tips

Setup Tips


Slow Rebound

Too slow and your fork will pack down and ride harsh.

If you increase your spring rate or air pressure, you will need to slow down your rebound


(Factory setting)

Average Rebound



Fast Rebound

Too fast and you will experience poor traction and wheel hop.

If you decrease your spring rate or air pressure, you will need to speed up your rebound setting.


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FOX Factory Inc.